Find coax cable velocity factor using an antenna analyser with SOL calibration
A common task is to measure the velocity factor of a sample of coaxial transmission line using an instrument that supports SOL calibration, an AIMuhf in this example.
Whilst this seems a trivial task with a modern antenna analyser, it seems to challenge many hams.
There are a thousand recipes, I am going to demonstrate just one that suits the instrument and application.
We will use a little test fixture that I made for measuring small components, and for which I have made test loads for SOL calibration. We will find the frequency where reactance passes through zero at the first parallel resonance of an O/C stub section, this is at a length of approximately λ/2 (a good approximation for low loss coaxial cables above about 10MHz).
The text fixture used for this demonstration is constructed on a SMA(M) PCB connector using some machined pin connector strip and N(M)-SMA(F) adapters to connect to the instrument.
Above is a pic of the test fixture with adapters (in this case on a AA-600). Continue reading Exploiting your antenna analyser #24
Last update: 5th April, 2018, 5:14 PM